In U.S. Pat. No. 5,533,412, a fluid flow meter is disclosed, comprising a conduit for flow of a fluid, a heating element being inside the conduit for generating a thermal pulse in the fluid and two-spaced apart sensors being inside the conduit and positioned downstream of the heating element, wherein the fluid carries a thermal pulse through the conduit to the two spaced apart sensors and wherein a transit time of the thermal pulse between the spaced apart sensors measures a fluid flow velocity. The fluid flow meter furthermore comprises circuitry being attached to the conduit for providing the heating element with a power pulse.
The techniques disclosed in U.S. Pat. No. 5,533,412 are not suitable for applications in which a channel is regularly replaced, for instance medical applications performed in sterile conditions such as intravenous infusion, anesthesia flow control and urinary catheters. During such medical interventions, typically a number of channels is consecutively used per patient. The fluid flow meter disclosed in U.S. Pat. No. 5,533,412 is too costly to be disposed every time the channel is replaced. Recycling of the fluid flow meter disclosed in U.S. Pat. No. 5,533,412 is not an economically feasible option either, given the efforts that will be required to employ the fluid flow meter for another channel.